code: def test_HandleMissingIndicator_NanNoNanInTrain_ExpectAsNanColumn(
      self,
  ):
      train = ["A", "B"]
      test = ["A", "B", np.nan]
  
      encoder = encoders.OneHotEncoder(
          handle_missing="indicator", handle_unknown="value"
      )
      encoded_train = encoder.fit_transform(train)
      encoded_test = encoder.transform(test)
  
      expected_1 = [[1, 0, 0], [0, 1, 0]]
      self.assertEqual(encoded_train.to_numpy().tolist(), expected_1)
  
      expected_2 = [[1, 0, 0], [0, 1, 0], [0, 0, 1]]
      self.assertEqual(encoded_test.to_numpy().tolist(), expected_2)
  
imports: import pandas
  from unittest import TestCase
  import numpy
  import tests.helpers
  import category_encoders
label_desc: Use image node_id 16 for calling the TestOneHotEncoderTestCase obj's underlying member method code with example usage: obj.test_HandleMissingIndicator_NanNoNanInTrain_ExpectAsNanColumn() without return types